The present invention relates to an audio signal processing system and, more particularly, to such a system having a balance control function in which a suitable listening position is electrically realized.
One of important control factors in a stereophonic audio system is a balance control of acoustic pressures and sound phase to realize a suitable listening position by the compensation of sound position images. In a car audio system in particular, not only the installed positions of speakers but also the listening position of a listener such as a driver are restricted, so that the distances from the listener to the respective speakers are in general different from each other. Therefore, it is required to perform a balance control such that the respective speakers exist imaginarily at the same distance from the listener.
However, the balance control system according to prior art merely controls the acoustic pressures at the listener's position. For example, when a balance control knob or key is operated in a left (or right) channel direction, only the acoustic pressure from a right (or left) channel speaker is controlled to become small. Thus, the conventional balance control system merely performs a control such that the left and right channel acoustic pressures actually received by the listener are made equal to each other.
In order to realize a balance control such that the respective speakers are located imaginarily at the same distance from the listener, not only the respective acoustic pressures reaching the listener but also the times for required by the sounds from the respective speakers to reach the listener, i.e. the phases of the respective sounds, have to be made coincident with each other.